There are two common ways to detect the presence of EtG, hair follicle test and a urine test. The basic difference between the two methods is the look-back period or the detection window. Here is how you can understand it:
The DNA laboratory extracts the genetic profiles of the alleged siblings and creates a siblingship index.
If the siblingship index is less than 1.00, this indicates non-relatedness. If the siblingship index is greater than 1.00, then the two tested individuals are more likely to be biological siblings. The higher the value of the siblingship index, the greater the likelihood that the two individuals are biological siblings.